Methods for Dopamine Modulation in Human Neurologic Diseases

ABSTRACT

A method of treating Parkinson&#39;s Disease, Huntington&#39;s Disease and the like, diseases with abnormal dopamine-neurotransmission, using small molecules administered systemically that penetrate into the central nervous system to inhibit the rate-limiting step of dopamine synthesis in the central nervous system, the conversion of L-tyrosine to L-3, 4-dihydroxyphenylalanine (L-DOPA) by tyrosine hydroxylase along with its cofactors tetrahydrobiopterin and iron (Fe + ).

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 16/965,466,filed Jul. 28, 2020, which is a National Stage Entry of InternationalApplication No. PCT/US2019/015143, filed Jan. 25, 2019, which claimspriority to and the benefit of U.S. Provisional Application Nos.62/623,348, filed Jan. 29, 2018, and 62/650,813, filed Mar. 30, 2018,which are expressly incorporated herein by reference in their entirety.

FIELD OF INVENTION

The present invention is a novel method of treating Parkinson's Disease,Huntington's Disease and the like, diseases with abnormaldopamine-neurotransmission, using small molecules administeredsystemically that penetrate into the central nervous system to inhibitthe rate-limiting step of dopamine synthesis in the central nervoussystem, the conversion of L-tyrosine to L-3, 4-dihydroxyphenylalanine(L-DOPA) by tyrosine hydroxylase along with its cofactorstetrahydrobiopterin and iron (Fe⁺).

BACKGROUND

Abnormalities in dopamine neurotransmission underlie movement disorders,as exemplified by Parkinson's and Huntington's diseases.

Parkinson's disease manifests initially as a movement disorder,progressing from tremors to the combination of muscle rigidity andakinesia. Widespread neurologic impairment follows. The biologichallmarks include loss of dopaminergic neurons in the brain (in thesubstantia nigra, largely in the pars compacta, within the basalganglia) with protein accumulation (Lewy Bodies) and oxidative stressthat impair function of the remaining cells (Fahn, S., Parkinsonism andRelated Disorders The 200-year journey of Parkinson disease: Reflectingon the past and looking towards the future, Parkinsonism Relat. Disord.46, 1-5 (2017), incorporated herein by reference in its entirety). Withloss of these neuronal cell bodies, their axonal projections into thecaudate nucleus and putamen of the midbrain are lost and/or lose theirability to synthesize and release dopamine.

The disease is the second most prevalent cause of neurologicdegeneration and loss of independent function, affecting millionsglobally (National Institute for Health and Care Excellence, Parkinson'sDisease in Adults: Diagnosis and Management. NICE Guideline NG71.(2017), incorporated herein by reference in its entirety).

This model of disease was reinforced in the 1970s with landmarkParkinson's studies demonstrating loss of dopaminergic neurons in thesubstantia nigra (Damier, P. et al., The substantia nigra of the humanbrain: II. Patterns of loss of dopamine-containing neurons inParkinson's disease, Brain 122, 1437-1448 (1999), incorporated herein byreference in their entirety). that correlated with reduction in dopaminelevels (Bernheimer et al., Brain Dopamine and the Syndromes ofParkinson, J. Neurol. Sci. 4, 145-148 (1973), incorporated herein byreference in its entirety). Post mortem studies linked theseneurochemical abnormalities to motor dysfunction (Hartmann, A.,Postmortem studies in Parkinson's disease, Dialogues Clin. Neurosci. 6,281-293 (2004), Hirsch et al., Melanized dopaminergic neurons aredifferentially susceptible to degeneration in Parkinson's disease,Nature 334, 345-348 (1988), incorporated herein by reference in theirentirety). Thus, medicines to increase dopamine levels in the caudatenucleus and putamen became the foundation of Parkinson's treatment,based on the rationale that pharmacologic levels of dopamine couldreverse the akinesia and improve motor function (Fahn, S., Parkinsonismand Related Disorders The 200-year journey of Parkinson disease:Reflecting on the past and looking towards the future, ParkinsonismRelat. Disord. 46, 1-5 (2017); National Institute for Health and CareExcellence, Parkinson's Disease in Adults: Diagnosis and Management.NICE Guideline NG71. (2017), incorporated herein by reference in theirentirety).

The current model of Parkinson's disease focuses on correcting theunderlying dopamine deficiency in the midbrain, by providing additionaldopamine or reducing its metabolism (National Institute for Health andCare Excellence. Parkinson's Disease in Adults: Diagnosis andManagement. NICE Guideline NG71. (2017), incorporated herein byreference in its entirety), as well as by providing stimulation to thebrain regions (electrically) that can stimulate these neural circuits tohelp relieve the movement disorder of Parkinson's disease (Bronstein etal., Deep brain stimulation for Parkinson disease an expert consensusand review of key issues, Arch. Neurol. 68, 165-171 (2011), incorporatedherein by reference in its entirety). In addition, therapies focus onrelated complications, such as depression, fatigue, sleepiness, impulsedisorders and loss of cognitive function, amongst others.

Thus the standard of care for Parkinson's—as recently summarized by theUnited Kingdom's NICE Treatment Guidelines—focused on providingdopaminergic support in the central nervous system, either by supplyingdopamine or reducing its metabolic breakdown (National Institute forHealth and Care Excellence. Parkinson's Disease in Adults: Diagnosis andManagement. NICE Guideline NG71. (2017), incorporated herein byreference in its entirety). Clinical trials demonstrate such approachesare associated with improved motor function and independence inactivities of daily living, though no clinical data show that any suchtherapy changes the underlying issues, natural history of, or theoverall progression of the disease. In fact, these studies show thatadditional dopaminergic support for patients with Parkinson's diseasemay only be palliative (The Parkinson Study Group, Levodopa and theProgression of Parkinson's Disease, N. Engl. J. Med. 351, 2498-2508(2004), incorporated herein by reference in its entirety). In parallel,the data show that whether patients are untreated or treated withstandard of care, neurologic dysfunction progresses to cognitiveimpairment, psychiatric disorders and other systemic manifestations(National Institute for Health and Care Excellence. Parkinson's Diseasein Adults: Diagnosis and Management. NICE Guideline NG71. (2017),incorporated herein by reference in its entirety).

Huntington's disease is caused by a genetic abnormality, typicallypresenting as a syndrome of abnormal, choreiform movements early indisease—also described as rapid, jerky, and repetitive involuntarymovements—with late stage disease often featuring relative bradykinesia,though this descriptor captures only one of the signs/symptoms and isused herein to represent the late stage of disease. Current hypothesesinclude dopamine as a central contributor in a biphasic pattern, withearly disease resulting from excess neurotransmission of dopamine andlate stage from dopamine depletion (Cepeda, C. et al., The Role ofDopamine in Huntington's Disease, Prog Brain Res 211, 235-254 (2014),Chen, et al., Dopamine imbalance in Huntington's disease: A mechanismfor the lack of behavioral flexibility, Front. Neurosci. 7, 1-14 (2013),incorporated herein by reference in their entirety).

Treatment of Huntington's rests largely on therapies that block dopamineneurotransmission across the synapse, doing so by inhibiting vesicularmonoamine transporter (VMAT type 2). With impaired vesicular uptake ofthe presynaptic dopamine, these axons cannot release the dopamine intothe intra-synaptic cleft. In addition to the effect of reducingchoreiform movements however, presynaptic cytosolic dopamine isincreased. Cytosolic dopamine is neurotoxic, and therefore, while itsincrease will negatively feedback on dopamine synthesis and lead totissue-level dopamine depletion, the intended effect, antagonizing VMAT2means that these presynaptic axons are exposed to dopamine toxicity.Such toxicity contributes to neuronal dysfunction and death, and eitheror both will shift the Huntington's patients from choreiform tobradykinetic state.

Therapeutics for Huntington's do not alter the natural history of thedisease, and all rest on VMAT inhibition (Teva Pharmaceuticals USA.Austedo, Prod. Label (2017), Neurocrine Biosciences, Ingrezza (packageinsert), (2017), Valeant International Bermuda. XENAZINE®(tetrabenazine) tablets, for oral use. Product Label (2015),incorporated herein by reference in their entirety).

Preclinical data show that dopamine is toxic to dopaminergic neurons,and that reduction of its synthesis protects these cells fromdysfunction and death.

A novel approach is proposed herein, drug treatment(s) to reducecellular dopamine production to protect neurons, and potentially restoreproper dopamine control systems.

SUMMARY OF THE INVENTION

In accordance with the present invention, compositions and methods areprovided that are effective in treating Parkinson's Disease and otherdiseases caused by reduced dopamine levels within neurons and/orabnormal dopamine-neurotransmission, exemplified by Huntington'sDisease. These compositions are easily administered by different routesincluding oral and can be given in dosages that are safe and provideantagonistic behavior and/or effects to inhibit the production or uptakeof dopamine.

This invention also relates to a correlation between a reduction indopaminergic cells of the substantia nigra (TH⁺ cells) and tissuedopamine.

In one embodiment, Parkinson's Disease and/or Huntington's Disease aretreated using small molecules administered systemically that penetrateinto the central nervous system to inhibit the rate-limiting step ofdopamine synthesis in the central nervous system, the conversion ofL-tyrosine to L-3,4-dihydroxyphenylalanine (L-DOPA) by tyrosinehydroxylase along with its cofactors tetrahydrobiopterin and iron (Fe⁺).

Antagonism of tyrosine hydroxylase decreases levels of aminergicneurotransmitters, such as norepinephrine, epinephrine, and dopamine.One such tyrosine hydroxylase antagonist is metyrosine (U.S. Pat. Nos.4,117,161, 2,868,818, Sjoerdsma, A. et al., Inhibition of CatecholamineSynthesis in Man with Alpha-Methyl-Tyrosine, and Inhibitor of TyrosineHydroxylase, The Lancet 286, 1092-1094 (1965), Engelman, K. et al.,Metabolism of alpha-methyltyrosine in man: relationship to its potencyas an inhibitor of catecholamine biosynthesis, J. Clin. Invest. 47,568-576 (1968), incorporated herein by reference in their entirety).This and other therapies taught herein are synthesized and used innative form(s) as well as with deuterium substituting for hydrogen inone or more locations.

To optimize patient compliance, many medicines are packaged in formsthat delay the release of the active entity after oral administration.

In one embodiment of the present invention, a tyrosine hydroxylaseinhibitor is administered as a treatment for Parkinson's disease and/orParkinsonism and/or Huntington's disease.

In some embodiments of the present invention, a tyrosine hydroxylaseinhibitor is administered as treatment of Parkinson's disease and/orParkinsonism and/or Huntington's disease initially at a nominal dosethat is gradually increased over days or weeks.

In some embodiments of the present invention, administration of atyrosine hydroxylase inhibitor is administered as treatment ofParkinson's disease and/or Parkinsonism and/or Huntington's disease andsupported by concomitant or intermittent administration of dopamineagonist therapy/therapies.

In some embodiments of the present invention, tyrosine hydroxylaseactivity is antagonized by administration of an inhibitor oftetrahydrobiopterin biosynthesis as treatment of Parkinson's diseaseand/or Parkinsonism and/or Huntington's disease.

In some embodiments of the present invention, a tyrosine hydroxylaseinhibitor is administered with an inhibitor of tetrahydrobiopterinbiosynthesis as treatment of Parkinson's disease and/or Parkinsonismand/or Huntington's disease.

In some embodiments of the present invention, a tyrosine hydroxylaseinhibitor is administered with an inhibitor of tetrahydrobiopterinbiosynthesis as treatment of Parkinson's disease and/or Parkinsonism andsupported by concomitant or intermittent administration of dopamineagonist therapy/therapies.

In some embodiments of the present invention, a tyrosine hydroxylaseinhibitor is administered with an inhibitor of tetrahydrobiopterinbiosynthesis as treatment of Parkinson's disease and/or Parkinsonismand/or Huntington's disease and supported by concomitant or intermittentadministration of VMAT2 inhibitor(s).

In some embodiments of the present invention, each of these treatmentregimens is administered as a combination with any or all of a dopamineagonist, a monoamine oxidase type B (MAO-B) stimulator andcatechol-O-methyltransferase (COMT) stimulator.

In some embodiments of the present invention, each of these therapeuticmolecules has one or more hydrogen atoms replaced with deuterium,strengthening the bond, slowing metabolism and improvingpharmacokinetics and pharmacodynamics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 . Catecholamine biosynthesis from tyrosine (5) to L-dopa (9) viatyrosine hydroxylase (7), also known as aromatic amino acid hydroxylase,the rate-limiting step, and then to dopamine (13) via aromatic aciddecarboxylase (11).

FIG. 2 . Neurotransmission via dopaminergic pathway, from thepre-synaptic axon terminal (60) to the post-synaptic dendrite (62).Major synthetic, metabolic and feedback control mechanisms arerepresented.

FIG. 3 . Examples of chemicals used for direct inhibition of tyrosinehydroxylase, in FIG. 3(a) AMPT shown with a representative conjugate,the methyl ester form, in FIG. 3(b) alternative tyrosine hydroxylaseinhibitors and in FIG. 3(c) template for side chain modification of theamino acid tyrosine hydroxylase inhibitors tyrosine and phenylalanine.For each and other embodiments taught herein, the R3 and R5 moietiesundergo substitution with halides, either at R3 or at both locations,which increases potency as a tyrosine hydroxylase inhibitor. Forembodiments based on these structures, methylation at RO increasespotency. Substitutions by halides at R3 or R3 with R5 to form dihalidesare additional embodiments of the invention.

FIG. 4 . Primary human metabolic pathway of alpha-methyl-p-tyrosine withexemplary deuteration sites.

FIG. 5 . Effect of chronic inhibition of dopamine synthesis with AMPT indopaminergic iPS cells originating from DJ-1 homozygous Parkinson'spatients treated with AMPT showing reduced oxidative stress, lowerlevels of oxidized dopamine, and blunted deposition of α-synuclein.

DETAILED DESCRIPTION

A biochemical hallmark of Parkinson's disease is loss of dopamine in thebasal ganglia, particularly with loss of the dopaminergic neuronal cellbodies in the substantia nigra pars compacta (SNpc) (Damier, P. et al.,The substantia nigra of the human brain: II. Patterns of loss ofdopamine-containing neurons in Parkinson's disease, Brain 122, 1437-1448(1999), Hirsch, E. et al., Melanized dopaminergic neurons aredifferentially susceptible to degeneration in Parkinson's disease,Nature 334, 345-348 (1988), incorporated herein by reference in theirentirety). While symptomatic benefit results from administration ofdopamine and dopaminergic therapies, such approaches do not appear tochange the course of disease (The Parkinson Study Group, Levodopa andthe Progression of Parkinson's Disease, N. Engl. J. Med. 351, 2498-2508(2004), incorporated herein by reference in its entirety). As depictedin FIG. 2 , dopaminergic neurotransmission from pre- to post-synapticterminal is controlled on several levels. Pre-synaptic dopaminesynthesis is controlled via effects on biopterin dependent enzymetyrosine hydroxylase (50) conversion of tyrosine (20) to L-dopa (22).Dopamine (24) in the cytosol is sequestered within vesicles (26) basedon VMAT2 activity, which prevents cellular toxicity. Upon stimulation,via membrane depolarization, vesicles fuse with the cell membrane (28)and dopamine is released into the synapse (30) via exocytosis. Inaddition to stimulating the post-synaptic membrane at D1 (32) and D2(34) receptors, pre-synaptic D2 (38) receptors serve auto-regulatoryfunction. The high levels of dopamine in the cleft result in rapidreuptake by the pre-synaptic terminal via DAT channels (36), with thatdopamine stored once again in vesicles driven by VMAT2 activity, andfree cytosolic dopamine (42) metabolized via MAO-B and COMT enzymes(44).

D1 and D2 receptors are G-protein coupled protein receptors (GCPR), withpost-synaptic D1 (32) and D2 (34) receptors having opposing effects ondendritic cAMP (58) activity. D1 stimulation increases cAMP (58) via thestimulatory G protein coupled Gs-adenyl cyclase complex (54), andthereby intracellular calcium, while D2 stimulation reduces cAMP (58)via the inhibitory G protein coupled Gi-adenyl cyclase complex (56).

In a state of excess dopaminergic drive starting at the axon terminal, adeficit in VMAT2 driven vesicular storage exposes the axon to toxic freeradicals formed from breakdown of cytosolic dopamine. The proteinα-synuclein (40) is known to be the major component of intracellularLewy Bodies, which serve as markers of disease progression as well asimpairing neuronal function. In addition, α-synuclein appears to playseveral roles in mitigation of the risk of dopamine toxicity within theaxon terminal, including (a) inhibition of tyrosine hydroxylase (50) andamino acid decarboxylase (52), (b) stimulating formation of vesicles fordopamine storage (26) and reducing the rate of DAT-mediated dopaminereuptake (36). α-synuclein also spares dendritic exposure to dopamine,as it blunts vesicular exocytosis of dopamine (28). In addition, bindingbetween α-synuclein and free cytosolic dopamine leads to reducedcellular exposure to dopaminergic free radicals, though at the cost ofprotofibril formation that hastens the development of Lewy Bodies. Thesemechanistic phenomena suggest that Lewy Body formation may representprotective neuronal mechanisms for brief exposure to toxic dopamine thatresult in additional pathologic effects when the mechanism remainsactive long-term.

VMAT2 deficiency whether due to genetic abnormality or altered geneexpression further exposes the neuron and its axon to dopamine toxicity.When dopamine is stored within the axonal vesicles, as it would be priorto exocytosis into the intrasynaptic cleft, it is protected againstoxidation. And that oxidation of dopamine is a major trigger leading toneuronal toxicity. As described below, while total dopamine is markedlydepleted, the per cell amount of dopamine is near normal in Parkinson'sdisease. Thus, the VMAT2 deficiency of Parkinson's means that thebalance between vesicular and cytosolic dopamine shifts towardssuper-normal cytosolic dopamine content, amplifying the amount ofoxidized dopamine and the risk of cellular and organelle (e.g.,mitochondrial) dysfunction and death from this toxic form of dopamine(Lohr, K. M. & Miller, G. W., VMAT2 and Parkinson's disease: harnessingthe dopamine vesicle, Expert Rev. Neurother. 14, 1115-1117 (2014),incorporated herein by reference in its entirety).

The physiology is similar for Huntington's disease patients treated withVMAT2 inhibitor(s). To prepare dopamine for synaptic release, VMAT2mediates its storage within axonal vesicles (26). Without that process,dopamine remains free within the cytosol of the axon (60) where itoxidizes a range of cellular targets and cannot be released. Thatoxidative stress contributes to cell dysfunction and death (Bernheimeret al., Brain Dopamine and the Syndromes of Parkinson, J. Neurol. Sci.4, 145-148 (1973), incorporated herein by reference in its entirety).While the VMAT2 inhibitor(s) protects the post-synaptic dendrite (62)from excess dopamine, it leads to loss of pre-synaptic function. Such isa hallmark of late stage Huntington's disease.

In untreated Huntington's disease, the pathophysiology starts withexcess dopaminergic activity, which is responsible for the choreiformmovements and with that chronic state, leads to the pre-synaptic axonfunction and viability adversely affected by dopamine-mediated toxicity.Reduction of dopamine synthesis is taught herein as a novel means toalter the natural history of disease and the symptomatic manifestations.

Current approaches resting on VMAT2 inhibition protect the post-synapticdendrites from toxicity and reduce choreiform movements. However, thisputs the presynaptic machinery at risk. Thus, taught herein is a novelapproach of blocking dopamine synthesis without compromising the abilityto store those smaller amounts of dopamine within the vesicles.

The complexity and risk from these control mechanisms are underscored byrecognition that the polymers deposited in mitochondrial impair energyproduction, further amplifying oxidative stress. Directly and/orindirectly, alpha-synuclein impairs neuronal function and increaseslikelihood of cell death.

To date, the precise trigger(s) for the development of sporadicParkinson's Disease is(are) unknown, though several genetic forms leadto similar pathology, with dopamine associated toxicity along withreduced dopamine stores resulting from loss of dopaminergic neurons.Thus, the genetic forms also are treated as a dopamine deficiency statethat must be reversed. This invention teaches a novel method fortreating Parkinson's disease in both subclinical and clinical states,reducing dopamine production and/or increasing its metabolism withinviable neurons.

Currently, the genetic basis for Huntington's Disease is known, thoughthe shift from the early choreiform to the late bradykinetic state isassociated with loss of dopaminergic neurons (Bernheimer et al., BrainDopamine and the Syndromes of Parkinson, J. Neurol. Sci. 4, 145-148(1973), incorporated herein by reference in its entirety). Neurotoxicityfrom free cytosolic dopamine is a driver of that shift in cellpopulation—both in untreated disease and VMAT2 inhibitor treateddisease. Thus, this invention teaches a novel method for treatingHuntington's disease in both early and late clinical states, reducingdopamine production and/or increasing its metabolism within viableneurons.

Disclosed herein are methods for reducing dopamine in the neurons of thecentral nervous system, in particular for neurons within the substantianigra pars compacta, as a treatment for patients with Parkinson'sDisease, including those identified with neurochemical abnormalitiesthat would be expected to evolve into overt Parkinson's Disease, as wellas for patients with Huntington's Disease, whether early or late indisease evolution, to slow, reverse and/or halt disease progression.

Based on metabolism of dopamine, the approaches could include any or allof the following: antagonism of tyrosine hydroxylase activity,antagonism of amino acid decarboxylase, stimulation of monoamine oxidasetype B activity and/or stimulation of catechol-O-methyltransferaseactivity. Because the amino acid decarboxylase relevant to Parkinson'sdisease and/or Parkinsonism and/or Huntington's disease—dopaminedecarboxylase—is not rate limiting in dopamine synthesis, this is not afocus of this invention. Therefore, taught herein are methods thatantagonize tyrosine hydroxylase, using direct enzymatic inhibitors aswell as using direct inhibitors of its required co-factor,tetrahydrobiopterin.

While total dopamine amounts are depleted, on a per cell basisParkinson's disease and Huntington's disease patients appear to maintainnormal amounts of dopamine synthesis. However, neurons cannot protectthemselves from dopamine toxicity even at these normal physiologiclevels, and therefore, would appear to be at heightened risk of toxicityfrom the pharmacologic levels produced by medicines (Meiser et al.,Complexity of dopamine metabolism. Cell Commun. Signal. 11, 1-18 (2013),Moon, H. E. & Paek, S. H. Mitochondrial Dysfunction in Parkinson'sDisease, Exp. Neurobiol. 24, 103-16 (2015), incorporated herein byreference in their entirety). With increase amount of alpha-synuclein,Parkinson's neurons can no longer protect themselves from dopaminetoxicity by sequestering it within intracellular vesicles (Perez, R. G.et al., A role for α-Synuclein in the Regulation of DopamineBiosynthesis, J. Neurosci. 22, 3090-3099 (2002), Venda et al.,α-Synuclein and dopamine at the crossroads of Parkinson's disease,Trends Neurosci. 33, 559-568 (2010), incorporated herein by reference intheir entirety). And because they suffer from mitochondrial dysfunction,the cells are exposed to oxidative stress (free radical generation) thatimpairs cellular function (Moon, H. E. & Paek, S. H., MitochondrialDysfunction in Parkinson's Disease, Exp. Neurobiol. 24, 103-16 (2015),incorporated herein by reference in its entirety). In the presence ofdopamine, this oxidative stress results in formation of alpha-synucleinprotofibrils (Conway, K. A., Kinetic Stabilization of thealpha-Synuclein Protofibril by a Dopamine-alpha-Synuclein Adduct,Science 294, 1346-1349 (2001), incorporated herein by reference in itsentirety). Formation of Lewy Bodies further impairs cellular function(Perez, R. G. et al, A role for α-Synuclein in the Regulation ofDopamine Biosynthesis, J. Neurosci. 22, 3090-3099 (2002), Venda et al.,α-Synuclein and dopamine at the crossroads of Parkinson's disease,Trends Neurosci. 33, 559-568 (2010), incorporated herein by reference intheir entirety). Pharmacologic treatment of Huntington's inhibits VMAT2,which reduces the capacity to store dopamine within vesicles and similarto in Parkinson's, results in a relative excess of dopamine in theneurons. These factors contribute to cell death (Ogawa et al., L-DOPAtreatment from the viewpoint of neuroprotection: Possible mechanism ofspecific and progressive dopaminergic neuronal death in Parkinson'sdisease, J. Neurol. 252, 23-31 (2005), incorporated herein by referencein its entirety).

Tyrosine hydroxylase, with its four isoforms, is the rate limitingenzyme in the synthesis of dopamine in the central nervous system(Meiser et al., Complexity of dopamine metabolism, Cell Commun. Signal.11, 1-18 (2013), Levitt, et al., Elucidation of the Rate-Limiting Stepin Norepinephrine Biosynthesis in the Perfused Guinea-Pig Heart, J.Pharmacol. Exp. Ther. 148, 1-8 (1965), incorporated herein by referencein their entirety), working with its cofactor tetrahydrobiopterin.

In one embodiment, the treatment is the tyrosine hydroxylase inhibitormetyrosine (Demser®, manufactured as the L-enantiomer), also known asalpha-methyl-p-tyrosine (AMPT).

In another embodiment, the treatment is a racemic mixture ofalpha-methyl-p-tyrosine.

In another embodiment, due to risk of nephrolithiasis during AMPT use, acombination of AMPT with a urinary alkalinizing agent is administered.

AMPT antagonizes tyrosine hydroxylase (Sjoerdsma et al., Inhibition ofCatecholamine Synthesis in Man with Alpha-Methyl-Tyrosine, and Inhibitorof Tyrosine Hydroxylase, The Lancet 286, 1092-1094 (1965), Engelman etal., Metabolism of alpha-methyltyrosine in man: relationship to itspotency as an inhibitor of catecholamine biosynthesis, J. Clin. Invest.47, 568-576 (1968), Nagatsu et al., Tyrosine Hydroxylase: The InitialStep in Norepinephrine Biosynthesis, J. Biol. Chem. 239, 2910-2917(1964), Udenfriend et al., Inhibitors of Purified Beef Adrenal TyrosineHydroxylase, Biochem Pharmacol 14, 837-845 (1965), incorporated hereinby reference in their entirety). An AMPT concentration of 10⁻¹ Minhibits tyrosine hydroxylase by 86% in guinea pig brain particlepreparations and by 50% at concentrations of 2.5×10⁻⁵ M in bovineadrenal gland preparations (Nagatsu et al., Tyrosine Hydroxylase: TheInitial Step in Norepinephrine Biosynthesis, J. Biol. Chem. 239,2910-2917 (1964), Udenfriend et al., Inhibitors of Purified Beef AdrenalTyrosine Hydroxylase, Biochem Pharmacol 14, 837-845 (1965), incorporatedherein by reference in their entirety). Various additional dosage formsand concentrations of AMPT are also effective, ranging between 500-2500mg/day.

Additional compounds represent other embodiments of the inventiontaught, based on data that establish their potency as inhibitors oftyrosine hydroxylase.

Each of these listed compounds in Tables 1A and 1B (shown below) areembodiments of the current invention. (See, Nagatsu et al., TyrosineHydroxylase: The Initial Step in Norepinephrine Biosynthesis, J. Biol.Chem. 239, 2910-2917 (1964), Udenfriend et al., Inhibitors of PurifiedBeef Adrenal Tyrosine Hydroxylase, Biochem Pharmacol 14, 837-845 (1965),incorporated herein by reference in their entirety).

TABLE 1A Amino acid analogs inhibiting tyrosine hydroxylaseConcentration Concen- for 50% tration % Compound Inhibition (M) (M)Inhibition L-tryptophan >1 × 10⁻³  10⁻⁴ 50 D-tryptophan 10⁻⁴ 0L-phenylalanine 2 × 10⁻⁴ 10⁻⁴ 78 D-phenylalanine >1 × 10⁻³  10⁻⁴ 7DL-p-fluoro-phenylalanine 10⁻⁴ 61 3-iodo-L-tyrosine 5 × 10⁻⁷3-chloro-L-tyrosine 1 × 10⁻⁵ 3-fluoro-DL-tyrosine 1 × 10⁻³3,5-diiodo-L-tyrosine 2 × 10⁻⁵ 3,5-dibromo-L-tyrosine 5 × 10⁻⁴α-methyl-L-tyrosine 2.5 × 10⁻⁵   10⁻⁴ 86 α-methyl-D-tyrosine >1 × 10⁻³ α-methyl-m-DL-tyrosine >1 × 10⁻³  2 × 10−4 92 α-methyl-DL-phenylalanine8 × 10⁻⁵ 3-iodo-α-methyl-DL-tyrosine 3 × 10⁻⁷3-bromo-α-methyl-DL-tyrosine 1.5 × 10⁻⁶   3-chloro-α-methyl-DL-tyrosine5 × 10⁻⁶ 3-fluoro-α-methyl-DL-tyrosine 2 × 10⁻⁴3-chloro-4-methoxy-α-methyl- 5 × 10⁻⁴ DL-phenylalanine

TABLE 1B Catecholamine analogs inhibiting tyrosine hydroxylaseConcentration Concen- for 50% tration % Compound Inhibition (M) (M)Inhibition dopamine 10⁻⁴ 56 L-norepinephrine  1 × 10⁻³ DL-norepinephrine2 × 10⁻⁴ 53 L-dopa 10⁻⁴ 68 D-dopa 10⁻⁴ 0 L-epinephrine 10⁻⁴ 35D-epinephrine 10⁻⁴ 47 3,4-dihydroxyphenyl-  1 × 10⁻³ acetamide3,4-dihydroxyphenyl-  2 × 10⁻⁵ 10⁻⁴ 84 propyl-acetamide (H-22/54)3,4-hydroxy-L-phenylalanine  2 × 10⁻³ 3,4-hydroxy-D-phenylalanine >4 ×10⁻³ α-methyl-3,4-dhydroxy-L- 1.5 × 10⁻³  phenylalanine (Aldomet)α-methyl-3,4-dhydroxy-D- >8 × 10⁻³ phenylalanine

Amino acid derivatives also act as tyrosine hydroxylase inhibitors(Udenfriend et al., Inhibitors of Purified Beef Adrenal TyrosineHydroxylase, Biochem Pharmacol 14, 837-845 (1965), incorporated hereinby reference in its entirety). For example, because most analogs ofphenylalanine and tyrosine inhibit tyrosine hydroxylase, embodimentsinclude any such analog, embodiments include racemic or L-amino acid inparticular. Additional potency results from α-methylation, and thus suchcompounds are taught herein as embodiments. Substitution at the3-position of the benzene ring of relevant amino acids with a halogenatom adds potency, and such compounds are taught herein as additionalembodiments. Substitution at both the 3 and 5 positions with halogenatoms are taught herein as additional embodiments of this invention.

Hoffman, incorporated herein by reference, describes several families oftyrosine hydroxylase inhibitors, though in the setting of cancer and notneurologic therapeutics (U.S. Patent Publication No. 2017/0056371,incorporated herein by reference in its entirety). These compounds areadditional embodiments of the invention taught herein, and include: oneor more of methyl (2R)-2-amino-3-(2-chloro-4 hydroxyphenyl) propanoate,D-tyrosine ethyl ester hydrochloride, methyl(2R)-2-amino-3-(2,6-dichloro-3,4-dimethoxyphenyl) propanoateH-D-Tyr(TBU)-allyl ester HCl, methyl(2R)-2-amino-3-(3-chloro-4,5-dimethoxyphenyl) propanoate, methyl(2R)-2-amino-3-(2-chloro-3-hydroxy-4-methoxyphenyl) propanoate, methyl(2R)-2-amino-3-(4-[(2-chloro-6-fluorophenyl)methoxy]phenyl) propanoate,methyl (2R)-2-amino-3-(2-chloro-3,4-dimethoxyphenyl) propanoate, methyl(2R)-2-amino-3-(3-chloro-5-fluoro-4-hydroxyphenyl) propanoate, diethyl2-(acetylamino)-2-(4-[(2-chloro-6-fluorobenzyl) oxy]benzyl malonate,methyl (2R)-2-amino-3-(3-chloro-4-methoxyphenyl) propanoate, methyl(2R)-2-amino-3-(3-chloro-4-hydroxy-5-methoxyphenyl) propanoate, methyl(2R)-2-amino-3-(2,6-dichloro-3-hydroxy-4-methoxyphenyl) propanoate,methyl (2R)-2-amino-3-(3-chloro-4-hydroxyphenyl) propanoate,H-DL-tyr-OME HCl, H-3,5-diiodo-tyr-OME HCl, H-D-3,5-diiodo-tyr-OME HCl,H-D-tyr-OME HCl, D-tyrosine methyl ester hydrochloride, D-tyrosine-omeHCl, methyl D-tyrosinate hydrochloride, H-D-tyr-OMe-HCl, D-tyrosinemethyl ester HCl, H-D-Tyr-OMe-HCl, (2R)-2-amino-3-(4-hydroxyphenyl)propionic acid, (2R)-2-amino-3-(4-hydroxyphenyl) methyl esterhydrochloride, methyl (2R)-2-amino-3-(4-hydroxyphenyl) propanoatehydrochloride, methyl (2R)-2-azanyl-3-(4-hydroxyphenyl) propanoatehydrochloride, 3-chloro-L-tyrosine, 3-nitro-L-tyrosine,3-nitro-L-tyrosine ethyl ester hydrochloride, DL-m-tyrosine,DL-o-tyrosine, Boc-Tyr (3,5-I2)-oSu, Fmoc-tyr(3-NO₂)—OH,α-methyl-L-tyrosine, α-methyl-D-tyrosine, and α-methyl-DL-tyrosine.Taught herein are dose ranges from 1 μg to 25 g per day for each ofthese compounds.

Additional embodiments of the invention use alternative tyrosinehydroxylase inhibitors. (See, Table 2).

TABLE 2 Tyrosine hydroxylase inhibitors taught herein as therapies forParkinson's disease and/or Parkinsonism substituted foralpha-methyl-p-tyrosine. Highest Prior Max Dose Chemical Formula MolarMass Dose Herein 3-iodotyrosine¹ C₉H₁₀INO₃ 307.09 g/mol — — bulbocapnineC₁₉H₁₉NO₄ 325.36 g/mol ~200 mg/d  2 mg/d aquayamycin² C₂₅H₂₆O₁₀ 486.47g/mol — 60 mg/d oudenone C₁₂H₁₆O₃ 208.25 g/mol ~1 g/d    10 g/d ¹3-Iodotyrosine is an intermediate in the synthesis of thyroid hormonesand its effects systemically preclude its delivery in this manner forthe intended central nervous system effect. ²The LD 50 in mice isreported at a dose as low as 12.5 mg/kg, the human equivalent of 1 mg/kgin 60 kg adult, which is therefore expected to be the maximum dose forthis invention.

Oudenone is a pentene based molecule identified from a needle-leaf treedemonstrated to inhibit tyrosine hydroxylase when directly measured, andalso reduce blood pressure in spontaneously hypertensive rats (Umezawa,H. et al. A New Microbial Product, Oudenone, Inhibiting TyrosineHydroxylase, J. Antibiot. (Tokyo) 23, 514-518 (1970), incorporatedherein by reference in its entirety). These investigators preparedsodium, potassium, calcium, magnesium and barium salts. Additionalembodiments include use of aquayamycin as a tyrosine hydroxylaseinhibitor, with potency near that reported for3-iodo-α-methyl-DL-tyrosine (Udenfriend et al., Inhibitors of PurifiedBeef Adrenal Tyrosine Hydroxylase, Biochem Pharmacol 14, 837-845 (1965),Ayukawa, S. et al. Inhibition of Tyrosine Hydroxylase by Aquayamycin, J.Antibiot. (Tokyo) 21, 350-353 (1968), incorporated herein by referencein their entirety). Taught herein are dose ranges from 1 μg to 25 g perday for each of these compounds.

As taught for oudenone, each of the embodiments taught herein areadministered as any of such salt forms.

Another embodiment impairs biosynthesis of tetrahydrobiopterin via sulfacompounds that cross the blood-brain-barrier, requisite for affectingtyrosine hydroxylase catalyzed dopamine production. Embodiments includesulfathiazole, sulfamethoxazole, sulfadiazine, sulfapyridine andsulfamethazine, each of which inhibits sepiapterin reductase, whichcatalyzes the final step in tetrahydrobiopterin synthesis, with IC50values below 100 nM (Haruki et al., Tetrahydrobiopterin biosynthesis asan off-target of sulfa drugs, Science 340, 987-991 (2013), incorporatedherein by reference in its entirety).

Examples of such embodiments are provided in Table 3, where for each,one embodiment is to start at low dose and titrate up to target ormaximally tolerated dose, as exemplified for alpha-methyl-p-tyrosine inTable 4.

TABLE 3 Examples of tyrosine hydroxylase inhibitors as replacements foralpha-methyl-p-tyrosine in example embodiments of the invention withmaximum daily doses to be used Chemical Highest Prior Dose Max DoseHerein sulfathiazole¹ 1.5 gm/d 1.5 gm/d  sulfamethoxazole 1.6 gm/d 16gm/d sulfadiazine   4 g/day 40 g/day sulfapyridine² 16 g/day(sulfasalazine) 160 g/d (sulfasalazine) sulfamethazine³ only used inlarge animals — ¹Sulfathiazole is not administered at dose higher thanpreviously used as any higher produces unacceptable side effect profile.²Sulfapyridine human exposure results from metabolism of sulfasalazine,which is given at doses up to 16 g/day and an embodiment uses thisdosing form for the intended effect. ³Sulfamethazine is only used inanimals with max dose of 250 mg/kg, the equivalent of approximately 17kg/day, indicating this compound is not viable as human therapeutic.

TABLE 4 alpha-methyl-p-tyrosine dosing schedule Daily Dose Visit Dosing(mg) (mg) Week 1: 25/25 50 Week 2: 50/50 100 Week 3: 100/100 200 Week 4:100/100/100 300 Week 5: 150/150/150 450 Week 6: 200/200/200 600 Week 7:250/250/250 750 Week 8: 300/300/300 900 Week 9: 400/400/400 1200 Week10: 500/500/500 1500

One of the effects of methotrexate is inhibition of dihydropteridinereductase (DHPR), an enzyme critical for formation oftetrahydrobiopterin, the cofactor required for tyrosine hydroxylaseinhibition. Thus another embodiment is use of methotrexate to inhibittyrosine hydroxylase activity indirectly.

Another embodiment is administering the target dose as the startingdose. For the embodiments that use any of these sulfa compounds, dosingstarts as recommended in approved labeling from the U.S. Food and DrugAdministration, with maximum doses an order of magnitude higher thanspecified for primary indications and/or prior pharmacology studies,with limitations noted in Tables 2 and 3.

Alpha-methyl-p-tyrosine can be dosed between 5 mg a day up to 2000 mgper day. Taught herein is the method of initiating therapy at low dosesthat are gradually increased, over days, weeks or months.

In one embodiment, doses start at a range of 1 mg daily up to 250 mgdaily would be the starting dose, and target dose would range from 100mg daily to 1000 grams daily. Table 4 is merely one example of how adose titration is completed, in this case of a patient started at 50 mgdaily and titrated to 1500 mg daily.

In another embodiment, doses start at frequencies of administration lessthan four times daily, including formulations up to once monthly viadepo methods, where depo refers to pharmaceutical method of injecting orimplanting a therapeutic agent into a tissue where it is absorbed moreslowly for prolonged maintenance of therapeutic drug levels in the body.In another embodiment, the amount of each dose is increased and inanother embodiment, the frequency of doses is increased, in order toincrease the total daily dosage.

In another embodiment, the amount of each dose and the frequency ofdosing are both used to increase the total daily drug dose. One of theways to explain this embodiment is shown in Table 4, usingalpha-methyl-p-tyrosine as the example, provided to show only onerepresentation of a dose titration schedule and one example of atyrosine hydroxylase antagonist. Other tyrosine hydroxylase antagonistsand doses would be known to a person of ordinary skill in the art.

In another embodiment, the tyrosine hydroxylase inhibitor isadministered using this graduated dosing approach while continuing thebackground therapy including dopaminergic medicines, including but notlimited to levodopa-containing agents, MAO-B inhibitors and/or COMTinhibitors, as well as dopamine agonists. For this embodiment, thedose(s) of the background medicine(s) are gradually reduced while thetyrosine hydroxylase inhibitor dose is increased or while the dose oftyrosine hydroxylase inhibitor is held constant.

In another embodiment, the standard dopaminergic therapies arediscontinued prior to initiation of therapy with tyrosine hydroxylaseinhibition.

In another embodiment, the standard dopaminergic therapies areintroduced as clinically required to help the patient(s) tolerate theincrease in the dose of tyrosine hydroxylase inhibitor.

In another embodiment, the standard dopaminergic therapies arere-introduced or the dose(s) augmented as required to stabilizepatient(s) clinically during the introduction and dose-titration of thetyrosine hydroxylase inhibitor(s) for a finite period of time.

In another embodiment, the use of deep brain stimulation is reduced tothe minimum required for clinical stability, with the stimulation usedmore or less as clinically indicated, and in some embodiments, withdrawn(even if not explanted).

In another embodiment, the tyrosine hydroxylase and/ortetrahydrobiopterin inhibitor(s) is(are) manufactured in modifiedrelease formulation(s) to reduce dosing frequency and/or control druglevels.

In some embodiments, diffusion systems are used, including use ofpolymer coatings that reduce the rate of dissolution followingingestion.

In some embodiments, active drugs are dissolved in a gelling agent.

In some embodiments, active drug(s) are administered in tablet(s) coatedwith semi-permeable membrane or laser-drilled holes, through either ofwhich drug release follows the absorption of water while passing throughthe gastrointestinal system.

In some embodiments, active drug(s) are manufactured within a matrixcomposed of polymers or lipids with delayed erosion by digestiveenzymes.

In some embodiments, active drug(s) are manufactured as liquids orliquid suspensions and administered intra-nasally, with starting dosesthen as low as 1/10 to 1/1,000 of those listed herein.

In some embodiments, the tyrosine hydroxylase inhibitor is administeredas its salt, ester, acid, gluconate, carbonate, anhydrous or free baseforms.

In other embodiments, the tyrosine hydroxylase inhibitor is substitutedwith other known tyrosine hydroxylase inhibitors, none of which aredescribed to date as treatments of Parkinson's disease or Parkinsonismin Tables 1 and 2.

In other embodiments, tyrosine hydroxylase activity is inhibitedindirectly via inhibition of tetrahydrobiopterin (Table 3) administeredin conjunction with direct tyrosine inhibitor(s).

In one such test, Parkinson's patients will be treated with one or more,in combination of succession, of the compounds taught herein for thisuse. Such a clinical trial will include both those patients early in thedisease, not yet treated with pharmacologic stimulators of dopamine, aswell as those already receiving such agents. Regulators may request suchstudies to be conducted separately on each population.

In such or any other clinical trials, standard measures of clinicalstatus may be used to assess outcome, such as the Unified Parkinson'sDisease Rating Scale. Functional tests evaluating ambulation are alsouseful outcomes for measurement, such as the 6 minute walk test, timedup and go test, and the like. Imaging of brain function, such as via PETor SPECT scanning, and the like, are used for understanding mechanismsof drug effect, and may be used in clinical testing. Other suchfunctional tests would be known to a person of ordinary skill in theart.

In other embodiments, Huntington's patients are treated with thetyrosine hydroxylate inhibitor(s) and/or tetrahydrobiopterin inhibitorwith VMAT2 inhibitor(s) during a transition from VMAT2 inhibition.

In Parkinson's disease, treatment to increase dopaminergic levels isassociated with adverse effects exemplified by tardive dyskinesia. Thisis often associated with peak drug levels. In the same patient(s), asthe dopamine and/or drug levels wane, the tardive dyskinesia is replacedby akinesia or bradykinesia, referred to as “off periods.” A focus ofdrug developers is levodopa-based therapies that produce more favorablepharmacokinetics to reduce these swings, as well as permit less frequentdosing.

Taught herein is deuteration of the therapies. Timmins and others teachhow deuterium's heavier molecular weight increases the strength of itsbonds compared to hydrogen atom(s). With that greater strength comesslower metabolism, longer half-life and less variability in drug levels(Timmins, G. S. HHS Public Access, Expert Opin Ther Pat 24(10),1067-1075 (2014), Gant, T. G. & Shahbaz, M. M., BenzoquinolineInhibitors of Vesicular Monoamine Transporter 2. (2013), (73), Sommer,A. et al., Formulations Pharmacokinetics of Deuterated BenzoquinolineInhibitors of Vesicular Monoamine Transporter 2. (2016), incorporatedherein by reference in their entirety). Such changes in pharmacokineticsare advantageous in clinical practice and taught herein for Parkinson's,Huntington's and other diseases/disorders with altered dopaminemetabolism treated with tyrosine hydroxylase inhibition.

The method of deuteration is taught herein, using AMPT as an example,with its metabolic pathway shown in FIG. 4 . Examples of deuterationtarget(s) for alpha-methyl-p-tyrosine (AMPT), shown as the metabolicpathway of AMPT in humans. Each R represents the site of a hydrogen atomin non-deuterated state, as well as a site for deuteration to inhibitthe rate of metabolism from one step to the next. 200:alpha-methyl-p-tyrosine (AMPT), 210: alpha-methyl-dopa (AMD), 220):alpha-methyl-dopamine (AMDA), 230: alpha-methyl-norepinephrine (AMNE).AMPT (200) is metabolized to alpha-methyl-dopa (210) then toalpha-methyl-dopamine (220) and finally to alpha-methyl-norepinephrine(230) (Engelman et al., Metabolism of alpha-methyltyrosine in man:relationship to its potency as an inhibitor of catecholaminebiosynthesis, J. Clin. Invest. 47, 568-576 (1968), Brogden et al.,alpha-Methyl-p-Tyrosine: A Review of its Pharmacology and Clinical Use,Drugs 21, 81-89 (1981), incorporated herein by reference in theirentirety). Delivered orally, the drug is well absorbed (˜69%) (Brogdenet al., alpha-Methyl-p-Tyrosine: A Review of its Pharmacology andClinical Use, Drugs 21, 81-89 (1981), incorporated herein by referencein its entirety) and relatively little of these metabolites arerecovered in the urine. Trace amounts of each can be detected (Engelmanet al., Metabolism of alpha-methyltyrosine in man: relationship to itspotency as an inhibitor of catecholamine biosynthesis, J. Clin. Invest.47, 568-576 (1968), incorporated herein by reference in its entirety).

In FIG. 4 , locations for deuteration are indicated by Rn, which areoccupied by hydrogen atoms in native state. Taught herein issubstitution at one or more of the Rn locations with a deuterium atom inplace of a hydrogen atom. Deuteration results in stronger bonds andtherefore slower reactions at that/those bond(s). Included is substationat R₅ in alpha-methyl-norepinephrine, as dehydroxylation at OR₅ producestrace amounts of alpha-methyl-tyramine.

Because Parkinson's and Parkinsonism feature presynaptic axonalcytosolic dopamine levels that are neurotoxic, whether the cause is dueto one or more of the known or unknown genetic causes, or the disease isidiopathic in etiology, the therapeutics taught herein are applicable togenetic or non-genetic causes, including as examples GBA, LRRK2, SNCA,VPS35, Parkin, PINK1, and DJ1.

A person of ordinary skill in the art would understand thatmodifications and substitutions could be made to the invention disclosedherein, as relates to the compounds, methods of use and means formeasuring the clinical effects.

What is claimed is:
 1. A method of treating neurodegenerative diseasesand disorders by administering a composition for antagonizing tyrosinehydroxylase.
 2. The method of claim 1, wherein the neurodegenerativecondition is Parkinson's disease.
 3. The method of claim 2, wherein theneurodegenerative condition is Parkinsonism.
 4. The method of claim 1,wherein the neurodegenerative condition is Huntington's disease.
 5. Themethod of claim 3, wherein the cause of Parkinsonism is progressivesupranuclear palsy.
 6. The method of claim 3, wherein the cause ofParkinsonism is multiple system atrophy.
 7. The method of claim 3,wherein the cause of Parkinsonism is diffuse Lewy Body disease.
 8. Themethod of claim 3, wherein the cause of Parkinsonism is drug-inducedParkinsonism.
 9. The method of claim 3, wherein the cause ofParkinsonism is Creutzfeldt-Jakob disease.
 10. The method of claim 3,wherein the cause of Parkinsonism is due to chronic brain trauma. 11.The method of claim 3, wherein the cause of Parkinsonism is linked to agenetic abnormality.
 12. The method of claim 3, wherein the geneticcause is GBA, LRRK2, SNCA, VPS35, Parkin, PINK1 and/or DJ1.
 13. Themethod of claim 4, wherein the Huntington's patient manifests choreiformand/or bradykinetic state(s).
 14. The method of claim 1, whereintyrosine hydroxylase activity is inhibited by a direct biochemicaleffect on that enzyme.
 15. The method of claim 1, wherein tyrosinehydroxylase activity is inhibited by an indirect biochemical effect onthat enzyme through inhibition of the biosynthesis of its cofactortetrahydrobiopterin.
 16. The method of claim 1, wherein tyrosinehydroxylase activity is inhibited by co-administration of a directinhibitor of that enzyme and indirectly through an antagonist of thebiosynthesis of that enzyme's cofactor, tetrahydrobiopterin.
 17. Themethod of claim 14, wherein the tyrosine hydroxylase inhibitor isalpha-methyl-p-tyrosine.
 18. The method of claim 17, whereinalpha-methyl-p-tyrosine is administered at a dose ranging from initialadministration at a range of 1 mg daily up to 250 mg daily with thetarget maintenance dose at a range from 100 mg daily to 1000 gramsdaily.
 19. The method of claim 17, wherein alpha-methyl-p-tyrosine isadministered intra-nasally.
 20. The method of claim 19, whereinintra-nasal alpha-methyl-p-tyrosine is administered at doses 1/10 to1/100 of oral doses listed in
 15. 21. The method of claim 17, whereinalpha-methyl-p-tyrosine is administered in the salt, ester, tartrate,gluconate, carbonate, anhydrous or free base forms.
 22. The method ofclaim 17, wherein alpha-methyl-p-tyrosine is administered in conjunctionwith levodopa, levodopa analog or dopaminergic containing medicines. 23.The method of claim 22, wherein the levodopa, levodopa analog ordopaminergic containing medication doses are adjusted during theinitiation and ongoing administration of alpha-methyl-p-tyrosine asclinically indicated.
 24. The method of claim 17, whereinalpha-methyl-p-tyrosine is administered in conjunction with MAO-Binhibitors.
 25. The method of claim 24, wherein the MAO-B inhibitorsdoses are adjusted during the initiation and ongoing administration ofalpha-methyl-p-tyrosine as clinically indicated.
 26. The method of claim17, wherein alpha-methyl-p-tyrosine is administered in conjunction withCOMT inhibitors.
 27. The method of claim 26, wherein the COMT-inhibitorsdoses are adjusted during the initiation and ongoing administration ofalpha-methyl-p-tyrosine as clinically indicated.
 28. The method of claim17, wherein alpha-methyl-p-tyrosine is administered in conjunction withany combination of levodopa, levodopa analog or dopaminergic containingmedicines, MAO-B inhibitors and/or COMT inhibitors.
 29. The method ofclaim 25, wherein the levodopa, levodopa analog or dopaminergiccontaining medication, MAO-B inhibitors and/or COMT inhibitors doses areadjusted during the initiation and ongoing administration ofalpha-methyl-p-tyrosine as clinically indicated.
 30. The method of claim17, wherein alpha-methyl-p-tyrosine is administered in conjunction withVMAT2 inhibitor(s).
 31. The method of claim 17, whereinalpha-methyl-p-tyrosine is deuterated in one or more positions wheremetabolism of alpha-methyl-p-tyrosine involves hydroxylation and/orcarbonylation.
 32. The method of claim 14, whereinalpha-methyl-p-tyrosine is administered in halide-substituted form. 33.The method of claim 32, wherein the halide is fluoride, chloride,bromide and/or iodide.
 34. The method of claim 32, wherein the halideform of alpha-methyl-p-tyrosine is deuterated in one or more positionswhere metabolism of alpha-methyl-p-tyrosine involves hydroxylationand/or carbonylation.
 35. The method of claim 33, wherein the halide isin the 3′ position of the benzene ring.
 36. The method of claim 33,wherein the halide is in the 5′ position of the benzene ring.
 37. Themethod of claim 33, wherein halide substation is in both the 3′ and 5′positions.
 38. The method of claim 37, wherein dihalide substitution ofalpha-methyl-p-tyrosine is with the same halide.
 39. The method of claim37, wherein dihalide substitution of alpha-methyl-p-tyrosine is with thedifferent halides.
 40. The method of claim 14, whereinalpha-methyl-p-tyrosine is administered in methyl-substituted form. 41.The method of claim 40, wherein the methylated form ofalpha-methyl-p-tyrosine is deuterated in one or more positions wheremetabolism of alpha-methyl-p-tyrosine involves hydroxylation and/orcarbonylation.
 42. The method of claim 14, wherein tyrosine hydroxylaseinhibition is via administration of one or more of methyl(2R)-2-amino-3-(2-chloro-4 hydroxyphenyl) propanoate, D-tyrosine ethylester hydrochloride, methyl(2R)-2-amino-3-(2,6-dichloro-3,4-dimethoxyphenyl) propanoateH-D-Tyr(TBU)-allyl ester HCl, methyl(2R)-2-amino-3-(3-chloro-4,5-dimethoxyphenyl) propanoate, methyl(2R)-2-amino-3-(2-chloro-3-hydroxy-4-methoxyphenyl) propanoate, methyl(2R)-2-amino-3-(4-[(2-chloro-6-fluorophenyl)methoxy]phenyl) propanoate,methyl (2R)-2-amino-3-(2-chloro-3,4-dimethoxyphenyl) propanoate, methyl(2R)-2-amino-3-(3-chloro-5-fluoro-4-hydroxyphenyl) propanoate, diethyl2-(acetylamino)-2-(4-[(2-chloro-6-fluorobenzyl) oxy]benzyl malonate,methyl (2R)-2-amino-3-(3-chloro-4-methoxyphenyl) propanoate, methyl(2R)-2-amino-3-(3-chloro-4-hydroxy-5-methoxyphenyl) propanoate, methyl(2R)-2-amino-3-(2,6-dichloro-3-hydroxy-4-methoxyphenyl) propanoate,methyl (2R)-2-amino-3-(3-chloro-4-hydroxyphenyl) propanoate,H-DL-tyr-OME HCl, H-3,5-diiodo-tyr-OME HCl, H-D-3,5-diiodo-tyr-OME HCl,H-D-tyr-OME HCl, D-tyrosine methyl ester hydrochloride, D-tyrosine-omeHCl, methyl D-tyrosinate hydrochloride, H-D-tyr-OMe-HCl, D-tyrosinemethyl ester HCl, H-D-Tyr-OMe-HCl, (2R)-2-amino-3-(4-hydroxyphenyl)propionic acid, (2R)-2-amino-3-(4-hydroxyphenyl) methyl esterhydrochloride, methyl (2R)-2-amino-3-(4-hydroxyphenyl) propanoatehydrochloride, methyl (2R)-2-azanyl-3-(4-hydroxyphenyl) propanoatehydrochloride, 3-chloro-L-tyrosine, 3-nitro-L-tyrosine,3-nitro-L-tyrosine ethyl ester hydrochloride, DL-m-tyrosine,DL-o-tyrosine, Boc-Tyr (3,5-I2)-oSu, Fmoc-tyr(3-NO2)-OH,α-methyl-L-tyrosine, α-methyl-D-tyrosine and/or α-methyl-DL-tyrosine.43. The method of claim 35, wherein the dose ranges are from 1 μg to 25g per day for each of these compounds.
 44. The method of claim 14,wherein the tyrosine hydroxylase inhibitor is one or more ofaquayamycin, bulbocapnine, oudenone, 3-iodotyrosine, L-tryptophan,L-phenylalanine, DL-p-fluoro-phenylalanine, and/or3,4-dihydroxyphenyl-propyl-acetamide (H-22/54).
 45. The method of claim44, wherein the dose ranges are from 1 μg to 25 g per day for each ofthese compounds.
 46. The method of claim 44, wherein each or any of thetyrosine hydroxylase inhibitors are deuterated at one or more siteswherein the halide form of alpha-methyl-p-tyrosine is deuterated in oneor more positions where metabolism of alpha-methyl-p-tyrosine involvedhydroxylation and/or carbonylation.
 47. The method of claim 15, whereinbiosynthesis of the tyrosine hydroxylase cofactor tetrahydrobiopterin isvia administration of one or more of sulfathiazole, sulfamethoxazole,sulfadiazine and/or methotrexate.
 48. The method of claim 47, whereinthe dose ranges are from 1 μg to 25 g per day for each of thesecompounds.
 49. The method of claim 15, wherein methotrexate isadministered less frequently than each day, including weekly, monthlyand/or intermittently based on clinical condition.
 50. The method ofclaim 17, wherein alpha-methyl-p-tyrosine is administered with a urinaryalkalinizing agent.
 51. The method of claim 50, wherein the alkalinizingagent is one or more of sodium bicarbonate, calcium carbonate, sodiumcitrate, potassium citrate and/or calcium citrate.
 52. The method ofclaim 51, wherein the dose ranges are from 5 to 300 mEq/day.
 53. Themethod of claim 1, wherein tyrosine hydroxylase inhibition is achievedvia combination of a tyrosine hydroxylase inhibitor with inhibitor oftetrahydrobiopterin biosynthesis.